Scanning Electron Microscope (SEM) images are used in various mapping and imaging applications, such as for inspection of semiconductor wafers. Several techniques are known in the art for three-dimensional (3D) mapping of samples using SEM images. For example, a conventional technique for inspecting semiconductor devices utilizes multiple sets of measurement data obtained by a SEM to determine the dimensional parameters of a semiconductor device. The SEM collects each set of data from a different angular orientation with respect to the device. The dimensional parameters of the semiconductor device are determined by analyzing the relationship between the SEM inspection angle and the collected data sets.
Another conventional method includes a 3D shape measurement in which detection signals from respective semiconductor elements are sequentially switched in synchronization with a scanning frame of an electron beam on a sample. The detection signals from the respective semiconductor elements can be sequentially recorded in recording addresses in a frame memory that correspond to the respective semiconductor elements. After four electron beam scanning sessions, each image data for 3D shape measurement is recorded in the frame memory, and processed for 3D shape measurement.
As yet another example, Marinello et al., describes dimensional measurements performed with a SEM using 3D reconstruction of surface topography through stereo-photogrammetry, in “Critical Factors in SEM 3D Stereo Microscopy,” Measurement Science and Technology, volume 19, no. 6, 2008, which is incorporated herein by reference.
Some conventional SEM mapping techniques use multiple detectors. For example, Harada et al. describe multi-detector SEM measurements in “A New CDSEM Metrology Method for Thin Film Hardmasks Patterns using Multiple Detectors,” Photomask Japan 2010 (published in BACUS News 27:2, February, 2011).